Conventional low-pressure compressors producing pressure ratios of 1.8 to 2.1 are characterized by low efficiency, large dimensions, weight and prime costs.
A rotary-vane blower disclosed in U.S. Pat. No. 6,113,370 which has a tubular rotor rotating at uniform speed to which are fixedly attached two first vanes. Two second vanes, forming with the first vanes four chambers for the working medium, perform inside the tubular rotor an oscillatory movement whereby the volume of the chambers is alternatively reduced and increased. This oscillatory movement is produced by a camming mechanism driven by the main shaft. While this blower works at an efficiency much higher than that of conventional blowers of all types, the camming mechanism with its high contact pressure is a serious drawback when high overpressures and high pressure ratios are desired.
Another known rotary-vane device is the Kauertz engine, in which the oscillating motion is obtained by a planetary gear arrangement including large and heavy overhanging cranks and levers, and including heavy vanes, all having large moments of inertia which, given the relatively high speeds of internal-combustion engines, produce intolerably high inertial loading, strictly limiting RPM and substantially impairing the usefulness of this design.